Now you have a list of user stories to be implemented. Before you could assigns all the stories to iteration, you need to identify the risk and value of stories to customers so that you can prioritize which story to be done first. A risk is any probable event or condition that have a potentially negative outcome on the project while value is how much the story benefits the user. After identifying the risks and value, plot it to form a quadrant graph. Form there, you can prioritize which to be done first or assign to early iteration and which will be done later.